Johnny Yen has an entertaining post about middle managers. I'm one of those, although I don't think of myself as a manager (and that word isn't in my title, thank god).
Junior managers are often drawn from the ranks because they are particularly good at their job, or at least some part of it. When was the last time a marginal performer was assessed for leadership and promoted on that basis? So you suck at making widgets. You might be a good leader anyway (Mario Mendoza, namesake of the dreaded Mendoza Line, became a coach after all).
Junior managers are usually left to their own devices to figure out how to be a good manager. Training? Expensive, and usually just risk management wearing a disguise. Role models? A bunch of people who used to be junior managers.
Good luck, fucker.
Now, a very short story: If you read the USA Today spread on Burger King a while back, you know how all the punditry is in gee-whiz shock mode because the new CEO, who has managed to see the company back to prominence, isn't a "food guy." But he is a wicked genius marketer, who realized the company can take one segment of its eatership (the 18-35 guys) and ride it to fame and fortune.
The moral: If you want good workers, hire good workers. If you want good managers, hire good managers. Don't assume that just because you have hired the best workers, you have a latent pool of the best managers, waiting to be found, sculpted or otherwise wrought.
The real moral: Johnny sees junior managers as people in search of a reason for having a job. This means they are often huge pains in the butt to everybody else. I see junior managers as a caste in crisis, a group whose villified performance is partly a result of changes in business culture from paramilitary organization to today's fuzzier system. The culture has changed, but the selection criteria and "training" regimen have not.
Maybe the time for a new system is now.